Colour kinescopes



Dec. 16, 1969 Ho c MlYASHlRo ET AL 3,434,862

COLOUR KINESCOPES Filed Dec. 20, 1967 2 Sheets-Sheet l loqr wlchmg rcuif Slum/0 lV/XlJl/E; Sww/ VII/P0020 I N VE N TORS "Dec.1

Filed Dec. 20, 1967 6. 1969 SHOICHI MIYASHIRO E COLOUR KINESCOPES 2 Sheets-Sheet 2 7 55403 F|G.5 21 F565 w:

I (D co GI] QUJ CD10 CD03 O :0 mm G) Colour Swiching Cnrcuir United States Patent U.S. Cl. 315-12 9 Claims ABSTRACT OF THE DISCLOSURE A colour kinescope is provided with an electron multiplier adapted to emit secondary electron beams when bombarded by a primary electron beam emitted by a single electron gun and a colour switching and deflecting grid is disposed between the electron multiplier and a fluorescent screen to deflect the secondary electron beams.

This invention relates to improvements relating to colour kinescopes or picture tubes.

Among prior colour kinescopes which have been utilised in colour television receivers are included shadow mask type colour kinescopes and Lawrence Tubes or Chromatrons (trade name). While the former, or the shadow mask type colour kinescopes have excellent colour fidelity, colouration and colour tone, there are such defects that the utilisation factor of the electron beam is low and that the brightness of the reproduced picture images is also low, due to the fact that a substantial number of electrons emitted by three electron guns is collected by the shadow mask.

The latter, the Chromatron tubes have been developed to eliminate these defects. They are not, however, satisfactory in providing a colour switching grid electrode operable at high potential and having a satisfactory high frequency characteristic in view of the necessity of deflecting electron beams of several kilovolts and hence of applying a high potential to the colour switching grid electrode.

Further in both types of prior kinescopes primary electrons emitted from the electron gun tend to incident obliquely against the fluorescent screen as the distance from its center increases with the result that primary electrons projected upon the peripheral portion of the fluorescent screen by the scanning section will become difficult to impinge upon the fluorescent materials of the desired colours (red, green and blue) thus causing colour shading in the reproduced picture.

Accordingly, it is an object of this invention to pro vide an improved colour kinescope or picture tube exhibiting increased brightness of fluorescence emitted from the fluorescent material and do not accompany any colour shading.

Another object of this invention is to provide a novel colour kinescope wherein the quantity of the primary elec tron beam emitted from the electron gun can be decreased and the operating life of the electron gun can be increased.

These and other objects can be achieved by providing a colour switching grid electrode between an electron multiplier device which emits secondary electron beams when irradiated by the primary electron beam from a single electron gun and a fluorescent screen arranged to be irradiated by the secondary electrons.

This construction results in the following advantages.

(1) As the electron multiplier device emits a much larger number of secondary electrons than the primary electrons, when irradiated by the secondary electron beams, the fluorescence brightness of the fluorescent material on the fluorescent screen will be greatly improved, thus increasing the brightness of the reproduced pictures.

(2) Even when the primary electron beam impinges obliquely upon the electron multiplier device only secondary electron beams are deflected by the colour switching grid electrode. Since the secondary electron beams are emitted perpendicularly to the fluorescent screen irrespective of the direction of advance of the primary electron beam when deflecting the secondary electron beams by the colour switching grid electrode, even in the peripheral portion of the fluorescent screen it is possible to cause secondary electrons to impinge upon the fluorescent material of the desired colour on the fluorescent screen in the same manner as in the central portion thereof. Consequently colour shading of the reproduced picture can be tron beams by the desired angle with low deflecting voltages.

The invention will be better understood by reference to the following detailed description taken in conjunction with the accompanying drawings in which:

' FIG. 1 shows a schematic longitudinal section of a colour kinescope embodying this invention;

FIG. 2 is an enlarged view of a portion of FIG. 1;

FIG. 3 shows a schematic longitudinal section of a modified colour kinescope according to this invention;

FIG. 4 is an enlarged view of an essential portion of FIG. 3 and FIGS. 5 and 6 show sectional views of another examples of the electron multiplier device and colour switching grid electrode employed in the colour kinescope of this invention.

Referring now to the accompanying drawing the colour kinescope illustrated in FIGS. 1 and 2 comprises a vacuum vessel 1 containing a single electron gun 8. In the vacuum vessel 1 and in front of the electron gun 8 is disposed an electron multiplier device 7 adapted to emit secondary electron beam 5 when an electron beam or emitted from the electron gun impinges upon it. The electron multiplier device 7 comprises a back plate 6 adapted to be irradiated by the primary electron beam or and an electron multiplier layer 5 having no aperture therein which functions to absorb energy from the primary electron beam tat-impinging upon the back plate 6 to emit the transmission secondary electron beams B. For example, the back plate 6 is made of an aluminum foil having a thickness of 500 A. and the electron multiplier layer 5 is formed by depositing upon the aluminum foil a layer of lithium fluoride to a thickness of 500 A., for example.

On the inner surface of a face plate 2 of the vacuum vessel 1 there is formed a layer 8 of a fluorescent ma terial which emits fluorescence when irradiated by the transmission secondary electron beams B. As shown in FIG. 2, this fluorescent screen 3 comprises mutually insulated metallic fine wires coated with fluorescent materials for producing red (R), green (G), and blue (B) colours respectively which are arranged in a plane in the order of RGBGRGBGR. A deflecting :and colour switching grid electrode 4 is disposed between the electron multiplier device 7 and the fluorescent screen 3. The deflecting grid electrode 4 is arranged in a plane parallel to the fluorescent screen 3. The spacing between them equals to 15 mm., for example, and the spacing between the deflecting grid electrode 4 and the electron multiplier layer 5 is 0.12 mm.'The deflecting grid electrode 4 is comprised by a plurality of parallel metal wires 40, 4b which are electrically connected alternately to divide said grid electrode into two components. The deflecting grid electrode 4 is connected to a colour switching circuit and the relative position between the deflecting grid electrode 4 and the fluorescent screen 3 is substantially the same as that utilized in Chromatrons.

The operation of the colour kinescope having the construction as above described is as follows:

The back plate 6 is supplied with a voltage of 4 kv. with respect to the cathode electrode of the electron gun 8, a base voltage of 4.24 k.v. is supplied to the colour switchinggiid electrode 4 and a voltage of 16 kv. is to the fluorescent screen 3. The primary electron beam on emitted from the electron gun 8 is deflected to the desired direction by a deflecting device 11 and then impinges upon the electron multiplier device 7. As a result, the electron multiplier layer 5 of the electron multiplier device 7 emits secondary electrons of the quantity much more than that of the primary electrons. Secondary electron beams p are collected by the fluorescent screen through the colour switching grid electrode 4. The secondary electron beams are also accelerated by a voltage of 12 kv. to impinge upon the fluorescent screen 3.

In the absence of any potential difference between adjacent grid electrode elements of the colour switching grid electrode 4 the secondary electron beams B will ad- Vance straightly toward the fluorescent material G as shown in FIG. 2. On the other hand, in the presence of a potential difference between adjacent grid electrode elements the secondary electron beams 13 will be deflected toward the grid electrode elements supplied with positive voltage to impinge upon the desired fluorescent material R or B.

As the colour switching grid electrode 4 is situated close to the electron multiplier device 7, the voltage necessary for switching the direction of deflection of the secondary electron beam [5 may be small.

As a result of various experiments it has been found that the smaller is the ratio l/P, the lower is the operating voltage require to be supplied to the colour switching grid electrode 4, where 1 represents the distance between the transmissive secondary electron emissive surface 5 and the colour switching grid electrode 4 and P the pitch of the colour switching grid electrode 4. It is also assumed that a voltage of 12 kv. is impressed across the back plate 6 and the fluorescent screen 3, a votlage of 240 v. is impressed across the back plate 6 and the colour switching electrode 4 and a voltage of 18 v. is used as the colour switching voltage.

It is desirable to supply to the back plate 6 of the electron multiplier device 7 a voltage which ensures a large emission of secondary electrons and prevents the primary electron beam a a emitted from the electron gun from penetrating through the electron multiplier device 7.

Should the primary electron beam at penetrate through the electron multiplier device 7, as this electron beam passes through the colour switching grid electrode 4 at higher energy than the secondary electron beams p it will not be influenced by the colour switching action of the grid electrode 4 so that it impinges upon the fluorescent material of the fluorescent screen 3 to emit fluorescence of undesirable colours.

Although in the above embodiment the electron multiplier device 7 was formed by depositing a secondary electron emissive material 5 on the supporting film 6 of aluminium the device 7 may also be fabricated by depositing a layer 5 of a secondary electron emissive substance on a film 6 of alumina (A1 0 Alternatively, the electron multiplier device 7 may also be fabricated by forming a supporting film consisting of a layer of aluminium, for example, upon a wire mesh, for example, a copper wire mesh and then depositing the secondary electron emissive substance on the aluminium layer. The latter construction makes easy fabrication of large electron multiplier surfaces.

Further, while the above described example was shown as comprising fine strips of fluorescent materials of three colours R, G and B, strips of two colours may also be used with the same result.

FIGS. 3 and 4 show another embodiment of a colour kinescope embodying this invention. Components shown in FIGS. 3 and 4 identical to those shown in FIGS. 1 and 2 are designated by the same reference characters and only those having different construction and function will be described. Although in the embodiment shown in FIGS. 1 and 2 the deflecting grid electrode 4 is contained in the'vacuum' vessel 1 and spaced from theelectron multiplier layer 5, in the embodiment shown in FIGS. 3 and 4 the deflecting grid electrode 4 is shown as being in contact with the electron multiplier layer 5. The deflecting grid electrode 4 is arranged in a plane spaced from the fluorescent screen by 12 mm. As the deflecting grid electrode 4 is in contact With the electron multiplier layer 5 the secondary electron beams B will be subjected to its deflecting action prior to their acceleration or while they are still in the low energy state. For this reason, the deflecting voltage supplied to the deflecting grid electrode 4 can be reduced. Thus, for example, when the potential difference between the back plate 6 and the fluorescent screen 3 is 12 kv., and that between the back plate 6 and the deflecting grid electrode 4 is 240 v., the deflecting voltage may be about 15 v.

FIGS. 5 and 6 illustrate modified constructions of the electron multiplier device and the colour switching grid electrode.

More particularly, in the construction shown in FIG. 5, insulator layers 21, calcium fluoride (CaF for example, are deposited on the side of a metal wire forming of a colour switching grid electrode 20 supporting film 22, made of aluminium oxide, for example, is formed on the insulator layer 21 and a conductive metallic film 23 deposited on the supporting film 22 on the side thereof facing the electron gun. Thereafter a transmission secondary electron emissive substance, for example lithium fluoride (LiF), is deposited on the supporting film 22 on the side thereof facing to the fluorescent screen whereby to form an integral structure of the electron multiplier device 27 and the colour switching grid electrode 20. When the strength of the structure is increased by increasing the thickness of the metallic film 23, the supporting film of aluminium oxide may be omitted.

In the embodiment shown in FIG. 6 a substrate 31 made of wire is coated with an insulator layer 32, and a metal film 33 acting as the colour switching grid electrode is deposited thereon on the side thereof facing to the fluorescent screen. A metal film 35 is coated upon a 500 mesh metal wire net 34 and on the surface thereof facing to the fluorescent screen is formed an electron multiplier layer 36 to form an electron multiplier device 37. The electron multiplier device and the colour switching grid electrode are assembled into a unitary structure by contacting the insulator layer 32 against the electron multiplier layer 36. The electron multiplier device 37 constructed as above described has an electron multiplier layer of large area.

With this construction since an insulator layer is formed between the color switching grid electrode and the electron multiplier layer, it is possible to maintain constant the spacing between the insulator layer and the electron multiplier layer and to reduce electrostatic capacitance by controlling the thickness of the insulator layer, thus simplifying the construction of the colour switching circuit.

Further the secondary electron emission ratio and the conduction of the back plate can be improved by forming a platinum layer of a thickness of about 10 A. on the back plate of the electron multiplier electrode.

While the principle of this invention has been described in connection with preferred embodiments thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What is claimed is:

1. A colour kinescope comprising:

a vacuum vessel;

an electron gun disposed in said vacuum vessel at one end thereof and adapted to emit a primary electron beam;

an electron multiplier device for emitting a transmission secondary electron beam on bombardment by said primary electron beam;

at deflecting and colour switching grid electrode adapted to deflect said secondary electron beams emitted from said electron multiplier device; and

a fluorescent screen including a plurality of fluorescent strips of diflerent colour which emit fluorescence when irradiated by the secondary electron beams deflected by said deflecting electrode;

said deflecting grid electrode being disposed between said electron multiplier device and said fluorescent screen.

2. A colour kinescope according to claim 1 wherein said fluorescent screen comprises fine red, blue and green strips.

3. A colour kinescope according to claim 1 wherein said deflecting grid comprises a plurality of parallel metal wires which are electrically connected alternately to divide said deflecting grid electrode into two components.

4. A colour kinescope according to claim 1 wherein said deflecting grid electrode is in contact through an insulator with said electron multiplier device.

5. A colour kinescope according to claim 4 wherein said insulator has a metallic core.

6. A colour kinescope according to claim 1 wherein said electron multiplier device comprises a back plate and a layer of a transmission secondary electron emissive substance which are laminated one upon the other.

7. A colour kinescope according to claim 6 wherein said layer of the secondary electron emissive substance consists of lithium fluoride and said back plate is made of aluminium.

8. A colour kinescope according to claim 4 wherein said deflecting grid electrode comprises a plurality of wires coupled to a metal layer.

9. A colour kinescope according to claim 1 wherein said electron multiplier device includes a substantially continuous layer of a transmission secondary electron emissive substance.

References Cited UNITED STATES PATENTS 2,899,600 8/1958 Bryan 31512 3,018,405 1/1962 Oxenham 315--12 3,024,385 3/1962 Burdick 315-l2 RODNEY D. BENNETT, JR., Primary Examiner JEFFREY P. MORRIS, Assistant Examiner 11.8. C1. X.R. 31392 

